Boris still 3% ahead in Mayor of London poll

According to my copy of The British Gemeral Election of 2010 by Dennis Kavanagh and Philip Cowley, at the General Election last year Labour won 36.6% of the vote in Greater London. The Conservatives won 34.5%.

According to YouGov, Labour are now 16% ahead in London. Does that mean that the Mayor of London Boris Johnson is dead in the water so far as his prospects of a second term are concerned?

The reasons for the difference between Labour's big lead at Westminster and almost non-existent lead for the mayoralty is partly down to the Liberal Democrat vote, which breaks in Johnson's favour,and partly down to there being more 'Labour for Boris' voters than there are 'Tories for Ken'.